Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi_4Ti_3O_（12） is a type of ferroelectric ceramics, which is supposed to replace leadcontaining cerami...Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi_4Ti_3O_（12） is a type of ferroelectric ceramics, which is supposed to replace leadcontaining ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi_4Ti_3O_（12） made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi_4Ti_3O_（12） ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800 ℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50 ℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100 ℃, r values peak can reach 205.40 at a frequency of 100 k Hz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values of Ea range from 0.52 to 0.68 e V. The dielectric properties of the sample sintered at 1 100 ℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi_4Ti_3O_（12） ceramics are a kind of dielectrics. Thus, Bi_4Ti_3O_（12） can be used in high-temperature capacitors and microwave ceramics.展开更多
采用溶胶-凝胶法制备了CaCu_(3)Ti_(4)O_(12)粉体,压制成型工艺和传统烧结工艺制备了CaCu_(3)Ti_(4)O_(12)陶瓷样品,研究了CaCu_(3)Ti_(4)O_(12)陶瓷的相结构与烧结工艺的关系,表征并讨论了CaCu_(3)Ti_(4)O_(12)陶瓷的负温度系数(NTC,Ne...采用溶胶-凝胶法制备了CaCu_(3)Ti_(4)O_(12)粉体,压制成型工艺和传统烧结工艺制备了CaCu_(3)Ti_(4)O_(12)陶瓷样品,研究了CaCu_(3)Ti_(4)O_(12)陶瓷的相结构与烧结工艺的关系,表征并讨论了CaCu_(3)Ti_(4)O_(12)陶瓷的负温度系数(NTC,Negative Temperature Coefficient)电阻特性,如电阻率(ρ)、热敏常数(B)、线性度和迟滞。实验结果证明:所制备的陶瓷坯体经950℃、1000℃、1050℃和1100℃烧结后可得到纯钙钛矿相的CaCu_(3)Ti_(4)O_(12)陶瓷;同时具有良好的NTC特性,室温电阻率(ρ25)为1.5×107Ω·cm,热敏常数为6223~6874 K;线性度和迟滞分别为1.50%和1.00%。展开更多
We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With a...We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With an increasing milling time, this particle size of mixture is gradually reduced, thus, we have mostly an amorphous phase. The BIT ceramics were duly obtained by sintering the synthesized powders at temperatures ranging from 850°C to 1000°C. The BIT ceramics sintered at 1020°C for 1 h, exhibiting a density with 7.52 g/cm3 of a crystaline phase and a dielectric of K = 288.11 (100 Hz), as well as a dielectric loss of 0.05 (100 kHz). The High-energy ball milling process is a promising way to prepare BIT ceramics. After the preparation of the BIT, we doped it with the Multi-Walled Carbon Nanotubes which are properly obtained by a chemical vapour deposition (CVD), using nickel as a catalyst, as well as using acetilene at 720°C, and then proceeded with the dielectric and optical measurements.展开更多
通过对角化364×364完全能量矩阵的理论方法,对掺杂在Bi_(4)Ge_(3)O_(12)晶体中的Er^(3+)的Stark能级和EPR参数进行了研究,同时,定量分析了高阶晶体场混合效应和J-J混合效应对EPR g因子的影响。研究结果表明:对Er^(3+)来说,最主要的...通过对角化364×364完全能量矩阵的理论方法,对掺杂在Bi_(4)Ge_(3)O_(12)晶体中的Er^(3+)的Stark能级和EPR参数进行了研究,同时,定量分析了高阶晶体场混合效应和J-J混合效应对EPR g因子的影响。研究结果表明:对Er^(3+)来说,最主要的J-J混合效应来源于多重态谱项2 K 15/2,其对EPR g因子的贡献约占2.5%,而最主要的高阶晶体场混合效应来源于第一激发多重态^(4)I_(13/2)和基态多重态^(4)I_(15/2)之间的晶体场混合,其对各向异性g因子中g⊥的贡献大致是g//的两倍(即g⊥约占0.21%,g//约占0.092%),其他更高阶的晶体场混合和J-J混合效应可以忽略不计。因此,对于Er^(3+)掺杂的络合物系统来说,只考虑基态多重态4 I 15/2对EPR g因子的贡献应该是一个很好的近似。展开更多
通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现...通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现先减小后增大的趋势,居里温度逐渐增加(Tc:483~494℃);压电常数和剩余极化强度都呈现出先增大后减小的趋势,其中x=0.035时压电常数和剩余极化强度同时达到最高值分别为d_(33)=18 p C/N,2P_(r)=16.5μC/cm^(2)。此外,BBT-BIT-0.035(Cu_(1/3)Nb_(2/3))陶瓷具有良好的热稳定性,在400℃/0.5 h下压电常数仍有14 p C/N,是起始值的82.4%,这有利于在较高温度的环境下工作。展开更多
In this study,(Cr_(1/3)/Ta_(2/3))non-equivalent co-doped Bi_(4)Ti_(3)O_(12)(BIT)ceramics were prepared to solve the problem that high piezoelectric performance,high Curie temperature,and high-temperature resistivity c...In this study,(Cr_(1/3)/Ta_(2/3))non-equivalent co-doped Bi_(4)Ti_(3)O_(12)(BIT)ceramics were prepared to solve the problem that high piezoelectric performance,high Curie temperature,and high-temperature resistivity could not be achieved simultaneously in BIT-based ceramics.A series of Bi_(4)Ti_(3-x)(Cr_(1/3)Ta_(2/3))_(x)O_(12)(x=0-0.04)ceramics were synthesized by the solid-state reaction method.The phase structure,microstructure,piezoelectric performance,and conductive mechanism of the samples were systematically investigated.The B-site non-equivalent co-doping strategy combining high-valence Ta^(5+)and low-valence Cr^(3+)significantly enhances electrical properties due to a decrease in oxygen vacancy concentration.Bi_(4)Ti_(2.97)(Cr_(1/3)Ta_(2/3))_(0.03)O_(12)ceramics exhibit a high piezoelectric coefficient(d_(33)=26 pC·N^(-1))and a high Curie temperature(TC=687℃).Moreover,the significantly increased resistivity(ρ=2.8×10^(6)Ω·cm at 500℃)and good piezoelectric stability up to 600℃are also obtained for this composition.All the results demonstrate that Cr/Ta co-doped BIT-based ceramics have great potential to be applied in high-temperature piezoelectric applications.展开更多
基金Funded by Hubei Provincial Department of Education(No.D20161006)
文摘Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi_4Ti_3O_（12） is a type of ferroelectric ceramics, which is supposed to replace leadcontaining ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi_4Ti_3O_（12） made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi_4Ti_3O_（12） ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800 ℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50 ℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100 ℃, r values peak can reach 205.40 at a frequency of 100 k Hz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values of Ea range from 0.52 to 0.68 e V. The dielectric properties of the sample sintered at 1 100 ℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi_4Ti_3O_（12） ceramics are a kind of dielectrics. Thus, Bi_4Ti_3O_（12） can be used in high-temperature capacitors and microwave ceramics.
文摘采用溶胶-凝胶法制备了CaCu_(3)Ti_(4)O_(12)粉体,压制成型工艺和传统烧结工艺制备了CaCu_(3)Ti_(4)O_(12)陶瓷样品,研究了CaCu_(3)Ti_(4)O_(12)陶瓷的相结构与烧结工艺的关系,表征并讨论了CaCu_(3)Ti_(4)O_(12)陶瓷的负温度系数(NTC,Negative Temperature Coefficient)电阻特性,如电阻率(ρ)、热敏常数(B)、线性度和迟滞。实验结果证明:所制备的陶瓷坯体经950℃、1000℃、1050℃和1100℃烧结后可得到纯钙钛矿相的CaCu_(3)Ti_(4)O_(12)陶瓷;同时具有良好的NTC特性,室温电阻率(ρ25)为1.5×107Ω·cm,热敏常数为6223~6874 K;线性度和迟滞分别为1.50%和1.00%。
基金We would like to thank to the institution below:UFC,LOCEM,UECE,CNPq,CAPES,FUNCAP,G.D.Saraiva acknowledges the support from MCT/CNPqEdital 14/2010(process 476569/2010-9)FUNCAP/Edital 02/2010(process 10293648-0)+1 种基金 FUNCAP/Edital 05/2009(process 186.01.00/09)The other authors acknowledge CNPq and FUNCAP for partial financial support.
文摘We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With an increasing milling time, this particle size of mixture is gradually reduced, thus, we have mostly an amorphous phase. The BIT ceramics were duly obtained by sintering the synthesized powders at temperatures ranging from 850°C to 1000°C. The BIT ceramics sintered at 1020°C for 1 h, exhibiting a density with 7.52 g/cm3 of a crystaline phase and a dielectric of K = 288.11 (100 Hz), as well as a dielectric loss of 0.05 (100 kHz). The High-energy ball milling process is a promising way to prepare BIT ceramics. After the preparation of the BIT, we doped it with the Multi-Walled Carbon Nanotubes which are properly obtained by a chemical vapour deposition (CVD), using nickel as a catalyst, as well as using acetilene at 720°C, and then proceeded with the dielectric and optical measurements.
文摘通过对角化364×364完全能量矩阵的理论方法,对掺杂在Bi_(4)Ge_(3)O_(12)晶体中的Er^(3+)的Stark能级和EPR参数进行了研究,同时,定量分析了高阶晶体场混合效应和J-J混合效应对EPR g因子的影响。研究结果表明:对Er^(3+)来说,最主要的J-J混合效应来源于多重态谱项2 K 15/2,其对EPR g因子的贡献约占2.5%,而最主要的高阶晶体场混合效应来源于第一激发多重态^(4)I_(13/2)和基态多重态^(4)I_(15/2)之间的晶体场混合,其对各向异性g因子中g⊥的贡献大致是g//的两倍(即g⊥约占0.21%,g//约占0.092%),其他更高阶的晶体场混合和J-J混合效应可以忽略不计。因此,对于Er^(3+)掺杂的络合物系统来说,只考虑基态多重态4 I 15/2对EPR g因子的贡献应该是一个很好的近似。
文摘通过传统固相法合成了具有超晶格结构的Ba Bi_(8)Ti_(7-x)(Cu_(1/3)Nb_(2/3))_(x)O_(27)(简称:BBT-BIT-x(Cu_(1/3)Nb_(2/3))共生陶瓷。结果表明,BBT-BIT-x(Cu_(1/3)Nb_(2/3))陶瓷的电学性能得到了有效地改善:随着x的增加,介电损耗呈现先减小后增大的趋势,居里温度逐渐增加(Tc:483~494℃);压电常数和剩余极化强度都呈现出先增大后减小的趋势,其中x=0.035时压电常数和剩余极化强度同时达到最高值分别为d_(33)=18 p C/N,2P_(r)=16.5μC/cm^(2)。此外,BBT-BIT-0.035(Cu_(1/3)Nb_(2/3))陶瓷具有良好的热稳定性,在400℃/0.5 h下压电常数仍有14 p C/N,是起始值的82.4%,这有利于在较高温度的环境下工作。
基金This work is financially supported by the National Natural Science Foundation of China(No.52172135)the Youth Top Talent Project of the National Special Support Program(No.2021-527-07)+1 种基金the Leading Talent Project of the National Special Support Program(No.2022WRLJ003)the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Nos.2022B1515020070 and 2021B1515020083).
文摘In this study,(Cr_(1/3)/Ta_(2/3))non-equivalent co-doped Bi_(4)Ti_(3)O_(12)(BIT)ceramics were prepared to solve the problem that high piezoelectric performance,high Curie temperature,and high-temperature resistivity could not be achieved simultaneously in BIT-based ceramics.A series of Bi_(4)Ti_(3-x)(Cr_(1/3)Ta_(2/3))_(x)O_(12)(x=0-0.04)ceramics were synthesized by the solid-state reaction method.The phase structure,microstructure,piezoelectric performance,and conductive mechanism of the samples were systematically investigated.The B-site non-equivalent co-doping strategy combining high-valence Ta^(5+)and low-valence Cr^(3+)significantly enhances electrical properties due to a decrease in oxygen vacancy concentration.Bi_(4)Ti_(2.97)(Cr_(1/3)Ta_(2/3))_(0.03)O_(12)ceramics exhibit a high piezoelectric coefficient(d_(33)=26 pC·N^(-1))and a high Curie temperature(TC=687℃).Moreover,the significantly increased resistivity(ρ=2.8×10^(6)Ω·cm at 500℃)and good piezoelectric stability up to 600℃are also obtained for this composition.All the results demonstrate that Cr/Ta co-doped BIT-based ceramics have great potential to be applied in high-temperature piezoelectric applications.
